Looking at the sellers registered business name etc, and the items he/they have for sale, I imagine they have a cheap source for cheap(er) parts and store them in a warehouse to flog on eBay. I maybe wrong though. I think it's safe to assume they're not an aftermarket performance parts expert.
But, on the other hand, their feedback rating is very good. However eBayers (myself included) often leave feedback when the parts have been delivered and examined, rather than after a few months of use.
However, it MAY be quite a good copy of an OK exhaust and with the notorious quality of Japspeed stuff, there's a chance it may even be better. If you can afford it and for the sake of £140, it might be worth a shot.
If you do get one, and it fits perfectly, and it sounds good, and the build quality is decent, please let us all know. I'll most probably be interested in getting myself one. Possibly...